Experiments on Mach-Wave Interactions in a Compressible Shear Layer

A potential technique for improving the growth rate of compressible shear layers is studied, in which a wavy-wall geometry is configured in a confined supersonic shear-layer facility that generates Mach waves in the flowfield. The major objective of this work is to evaluate a numerical model that predicts the growth properties of a three-way resonant interaction of these spatial Mach waves with duct acoustic waves and Kelvin-Helmholtz waves excited artificially or naturally within the shear layer. Measurements show that a tuned pure tone excitation of Kelvin-Helmholtz waves couples with the wavy-wall-induced disturbances and duct acoustic waves to produce local shear-layer growth rates that are approximately 50% higher than the natural, smooth-walled baseline case. The conditions for optimum growth rates are in general concurrence with numerical predictions. In this study the flow physics of a compressible shear layer in a wavy-wall environment was investigated with mean and fluctuating flowfield measurements, as well as schlieren visualizations